Our laboratory is broadly interested in both genetic and epigenetic modifications associated with exposure and cancer. Epigenetic modifications, including DNA methylation, are being increasingly recognized as is being recognized as important determinants of gene transcriptional regulation that have both heritable and acquired characteristics. Aberrant DNA methylation patterns are among the earliest and most common events in carcinogenesis and recent studies suggest that the epigenetic profile of DNA from a surrogate tissue, peripheral blood, may differ between women with active ovarian cancer compared to women without disease. We have employed genome-wide profiling of DNA methylation in peripheral blood samples from more than 900 women in order to investigate whether the pattern of DNA methylation is associated with breast cancer risk. We have identified a number of methylation sites that are associated with increased risk and are continuing data analysis. A second form of epigenetic modification is miRNA expression. Altered miRNA expression is a central feature of cancer and miRNA expression signatures have been shown to be associated with diagnosis, stage, prognosis, and response to treatment. Expression patterns for cancer show high tissue specificity making them potential markers for cancer screening. Breast cancer specific miRNAs have been shown to correlate with stage, vascular invasion, proliferative index, and ER/PR status. Recently, sufficient levels of miRNAs have been found in human plasma and serum to permit profiling, with sufficient power to distinguish men with metastatic prostate cancer from men without cancer and women with ovarian cancer. We have recently completed assays on more than 400 serum samples from cases and non-cases using the Sister Study cohort and are in the process of data analysis.